The present disclosure relates to digital-to-analog converters (DACs) and more particularly to placement of the current sources for the digital-to-analog converters in order to maximize linearity performance.
Digital to Analog converters (DACs) are ubiquitous in electronics where a digital signal is converted into an analog signal, e.g., for output or transmission. For example, in order to implement human-computer interfaces such as display monitors and audio outputs, computer systems employ DAC circuits, which convert digital vectors or addresses to an analog voltage or current. Digital to analog converters are used in many applications within integrated circuits (ICs) to control, tune, calibrate, or test larger and more complex systems. Some examples include audio output systems, radio frequency transmitters, temperature converters, etc. Rapid development of a digital signal processing technology results in an obvious demand for a high-speed/high-precision DACs. A high-speed DAC generally is a current source DAC, and a high precision requires good matching between unit current sources. There is a myriad of designs for DACs, and the designs may vary depending on the application and performance requirements.
In addition, the trend in microelectronics is the continued creation of smaller and smaller devices. As the devices become smaller, variations in the fringe of each shape of a device become a larger portion of the performance characteristics of the device and cause variations in the performance of a circuit dependent on the device. This is particularly important in circuits that convert from one signal domain to another, such as DACs, where precision in the conversion is required. Variation in the output signal as compared to an ideal response is known as a differential non-linearity (DNL) of the converted output signal.